The reactions of neutral and protonated nitrogen radicals (aminyl and aminium cation radicals, respectively) generated in mild and controlled reactions from N-hydroxypyridine-2-thione carbamates will be studied. Methods for producing both mono- and dialkyl substituted nitrogen radicals will be developed. Nitrogen radicals containing remote double bond cyclize to give five- and six- membered rings, and the influence of solvent and additives on the yields and stereoselectivities of these reactions will be studied. Methods for trapping the carbon radical intermediates formed in the cyclization reactions will be developed; these methods will be useful for other radical based synthetic methods. To demonstrate the utility of the methods, biologically active alkaloids will be synthesized by routes that incorporate the nitrogen radical cyclizations to build the skeletons. Ancillary studies will include the application of aminium radicals for remote functionalization of carbon atoms in substrates containing acid sensitive groups and investigations of new methods for generating nitrogen radicals by additions of carbon radicals to imines. The nitrogen centered radical cyclization will provide convenient and rapid enter to simple and complex alkaloid families and thus will be useful in the synthesis of a variety of biologically active and medicinally important compounds.